How do I fix opacity issues with overlapping fade objects?

In my project, I have a dialogue box with a separate "arrow" object pointing to the speaker. The two sprites overlap, and they are set to fade out simultaneously. When they fade out together, there is a spot where the opacity appears twice as high because the box and arrow are overlapping. I tried playing with blend modes, but I had no luck. Does anyone have an idea for a workaround? Thanks!